Reformer for fuel cell, and fuel cell system comprising the same

ABSTRACT

A reformer for a fuel cell system includes a heating source for generating heat by a reaction of a fuel and an oxidant using an oxidizing catalyst, and a reforming reaction part for generating hydrogen by a reforming catalyst reaction. The oxidizing catalyst includes a solid acid, including a strong acid ion and an inorganic oxide, and a platinum-based metal. The reformer for a fuel cell system can start a fuel oxidation catalyst reaction at a low temperature with the heating source having a simplified structure.

CROSS-REFERENCES TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

This application claims priority to and the benefit of Korean PatentApplication No. 10-2007-0014417 filed in the Korean IntellectualProperty Office on Feb. 12, 2007, and Korean Patent Application No.10-2007-0068111 filed in the Korean Intellectual Property Office on Jul.6, 2007 the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a reformer for a fuel cell system and afuel cell system including the same.

(b) Description of the Related Art

A fuel cell is a power generation system for producing electrical energyusing a hydrocarbon-based fuel.

Representative exemplary fuel cells include a polymer electrolytemembrane fuel cell (PEMFC) and a direct oxidation fuel cell (DOFC).

The polymer electrolyte membrane fuel cell (PEMFC) has been recentlydeveloped. The PEMFC has power characteristics that are superior tothose of conventional fuel cells, as well as a lower operatingtemperature and faster start and response characteristics. Because ofthis, the PEMFC can be applied to a wide range of applications such asfor portable electrical power sources for automobiles, distributed powersources for houses and public buildings, and small electrical powersources for electronic devices.

Such a polymer electrolyte membrane fuel cell system is composed of astack for a fuel cell body (hereinafter, for convenience referred to asa “stack”), a reformer that reforms the fuel to generate the hydrogengas and supplies the hydrogen gas to the stack, and an oxidant supplierfor supplying an oxidant gas to the stack. The stack generateselectrical energy through an electrochemical reaction of a reformed gassupplied from the reformer and an oxidant gas supplied from the oxidantsupplier.

The reformer includes a heating source for generating heat through acatalytic oxidizing reaction of the fuel, and a reforming reaction partfor generating a reformed gas from the fuel through a reforming catalystreaction of the fuel by the heat. In a conventional reformer, anoxidizing catalyst is required to be preheated at high temperature sinceoxidization of the fuel gas by the oxidizing catalyst occurs at hightemperature in a heating source of the reformer. Therefore, high heatefficiency is required in a fuel cell system.

SUMMARY OF THE INVENTION

The present invention provides an improved reformer and an improved fuelcell system including the reformer.

One embodiment of the present invention provides a reformer for a fuelcell system that can start a fuel oxidation catalyst reaction and has asimplified structure.

Another embodiment of the present invention provides a fuel cell systemincluding the reformer.

According to one embodiment of the present invention, provided is areformer for a fuel cell system that includes a heating source forgenerating heat by a reaction of a fuel and an oxidant using anoxidizing catalyst; and a reforming reaction part for generatinghydrogen by a reforming catalyst reaction. The oxidizing catalystincludes a solid acid which includes a strong acid ion and an inorganicoxide, and a platinum-based metal.

The platinum-based metal may include at least one selected from thegroup consisting of Pt, Pd, Ru, Rh, and combinations thereof. Theinorganic oxide includes an oxide of an element selected from the groupconsisting of Zr, Al, Ti, Si, Mg, Zn, and combinations thereof.

The strong acid ion may include at least one selected from the groupconsisting of a sulfate ion, a phosphate ion, and combinations thereof.

The platinum-based metal may be supported on the solid acid.

The oxidizing catalyst includes more than 0.5 parts by weight and lessthan or equal to 50 parts by weight of the platinum-based metal based on100 parts by weight of the oxidizing catalyst. According to oneembodiment, the oxidizing catalyst includes 1 to 5 parts by weight ofthe platinum-based metal based on 100 parts by weight of the oxidizingcatalyst. The oxidizing catalyst includes 10 to 70 parts by weight ofthe solid acid based on 100 parts by weight of the oxidizing catalyst.According to one embodiment, the oxidizing catalyst includes 20 to 60parts by weight of the solid acid based on 100 parts by weight of theoxidizing catalyst.

The oxidizing catalyst may further include a carrier supporting theplatinum-based metal and the solid acid. The carrier may be selectedfrom the group consisting of Al₂O₃, TiO₂, SiO₂, ZrO₂, MgO, andcombinations thereof. According to one embodiment, Al₂O₃ may beappropriate.

When the oxidizing catalyst further includes the carrier, the oxidizingcatalyst includes less than 89.5 parts by weight of the carrier based on100 parts by weight of the oxidizing catalyst. According to oneembodiment, the oxidizing catalyst includes 35 to 80 parts by weight ofthe carrier based on 100 parts by weight of the oxidizing catalyst.

The oxidizing reaction of the fuel by the oxidizing catalyst starts at atemperature of more than or equal to 90° C.

In the reformer according to another embodiment of the presentinvention, the heating source includes a first reacting region thatincludes a platinum-based catalyst including a solid acid which includesa strong acid ion and an inorganic oxide, and a platinum-based metal;and a second reacting region including a non-platinum-based catalyst.

The first and second reacting regions may be sequentially disposed.

The fuel and oxidant may be sequentially supplied to the first reactingregion and then to the second reacting region.

The platinum-based catalyst and non-platinum-based catalyst may beincluded in a volume ratio of 1:1 to 1:5.

The platinum-based metal may be selected from the group consisting ofPt, Pd, Ru, Rh, and combinations thereof.

The inorganic oxide may include an oxide of an element selected from thegroup consisting of Zr, Al, Ti, Si, Mg, Zn, and combinations thereof.

The strong acid ion may include at least one selected from the groupconsisting of a sulfate ion, a phosphate ion, and combinations thereof.

The platinum-based metal may be supported on the solid acid.

The platinum-based catalyst may include more than 0.5 parts by weightand less than or equal to 50 parts by weight of the platinum-based metalbased on 100 parts by weight of the oxidizing catalyst, and 10 to 70parts by weight of the solid acid based on 100 parts by weight of theplatinum-based catalyst.

The platinum-based catalyst may further include a carrier supporting theplatinum-based metal and solid acid.

The carrier may be selected from the group consisting of Al₂O₃, TiO₂,SiO₂, ZrO₂, MgO, and combinations thereof.

The carrier may be included in an amount of less than 89.5 parts byweight based on 100 parts by weight of the platinum-based catalyst.

The non-platinum-based catalyst may include a metal oxide includingCeO₂, MO (wherein M is a transition element), and CuO.

The M may be selected from the group consisting of Ni, Co, Fe, andcombinations thereof.

The non-platinum-based catalyst may include 10 to 30 parts by weight ofCeO₂, 0.1 to 5 parts by weight of MO, and 1 to 10 parts by weight ofCuO.

The non-platinum-based catalyst may further include ZrO₂.

Herein, the non-platinum-based catalyst may include 5 to 20 parts byweight of ZrO₂, 5 to 20 parts by weight of CeO₂, 0.1 to 5 parts byweight of MO, and 1 to 10 parts by weight of CuO.

The non-platinum-based catalyst may be supported on a carrier selectedfrom the group consisting of Al₂O₃, TiO₂, SiO₂, cordierite, andcombinations thereof.

According to another embodiment of the present invention, provided is afuel cell system that includes the above reformer, at least oneelectricity generating element for generating electrical energy by anelectrochemical reaction of hydrogen and an oxidant, a fuel supplier forsupplying a fuel to the reformer, and an oxidant supplier for supplyingan oxidant to the reformer and the electricity generating element.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention, and many of the attendantadvantages thereof, will be readily apparent as the same becomes betterunderstood by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings in which likereference symbols indicate the same or similar components.

FIG. 1 is a schematic diagram showing the structure of a fuel cellsystem according to another embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a stack structure for thefuel cell system illustrated in FIG. 1.

FIG. 3 is a graph showing temperature changes inside the heating sourceincluding the oxidizing catalyst according to Example 1.

FIG. 4 is a graph showing temperature changes inside the heating sourceincluding the oxidizing catalyst according to Example 15.

FIG. 5 is a graph showing temperature changes inside the heating sourceaccording to Reference Example 1.

FIG. 6 is a graph showing temperature changes inside the heating sourceaccording to Example 17.

FIG. 7 is a graph showing temperature changes inside the heating sourceaccording to Example 18.

DETAILED DESCRIPTION OF THE EMBODIMENTS

A reformer for a fuel cell system according to one embodiment includes aheating source for generating heat by a reaction of a fuel and anoxidant using an oxidizing catalyst, and a reforming reaction part forgenerating hydrogen by a reforming catalyst reaction. The oxidizingcatalyst includes a solid acid which includes a strong acid ion and aninorganic oxide, and a platinum-based metal.

The strong acid ion lets the inorganic oxide have a strong acid site onthe surface thereof. The strong acid ion strongly binds with theinorganic oxide and thereby the surface of the inorganic oxide becomesthermally stable.

The solid acid is stronger than 100% H₂SO₄ and is therefore referred toas a solid super acid. It also has both a Lewis acid site and a Bronstedacid site. The solid acid does not cause corrosion of a reactor and canbe repeatedly used, and also its product can be easily separatedcompared to a conventional liquid super acid. Therefore, it does notcause acid waste problems.

When the platinum-based metal is supported on the solid acid, theactivity of the platinum-based catalyst can be improved because thesolid acid is a super acid and has a relatively large specific surfacearea (generally over 80m²/g).

When the oxidizing catalyst is used for a catalyst for a heating sourceof a reformer for a fuel cell system, a starting temperature of thereaction of a fuel and an oxidant by the oxidizing catalyst can bereduced. The reaction of a fuel and an oxidant by the oxidizing catalystis processed as follows: a fuel is adsorbed onto the oxidizing catalystand then the adsorbed fuel is oxidized. When the oxidizing catalyst isused for a catalyst for a heating source of a reformer for a fuel cellsystem, the fuel is adsorbed onto the acid site of the solid acid of theoxidizing catalyst. Since the solid acid is a super acid, the fueladsorbed onto the solid acid has strong polarity. Due to the polarity ofthe absorbed fuel, the activation energy for oxidizing the fuel can bereduced, and the oxidation reaction of the fuel can be started at a lowtemperature of 90° C.

The term “platinum-based metal” in the specification and the claimsmeans platinum group metal. The platinum-based metal according to anembodiment of the present invention includes at least one selected fromthe group consisting of Pt, Pd, Ru, Rh, and combinations thereof.According to one embodiment, Pt may be appropriate.

The inorganic oxide includes an oxide of an element selected from thegroup consisting of Zr, Al, Ti, Si, Mg, Zn, and combinations thereof.According to one embodiment, Zr oxide may be appropriate for theinorganic oxide.

The strong acid ion includes at least one selected from the groupconsisting of sulfate ion, phosphate ion, and combinations thereof.

The oxidizing catalyst includes more than 0.5 parts by weight and lessthan or equal to 50 parts by weight of the platinum-based metal based on100 parts by weight of the oxidizing catalyst. According to oneembodiment, the oxidizing catalyst includes 1 to 5 parts by weight ofthe platinum-based metal based on 100 parts by weight of the oxidizingcatalyst. When the amount of the platinum-based metal is not more than0.5 parts by weight, the oxidizing catalyst activity is reduced and thusthe starting temperature of the fuel oxidation by the oxidizing catalystcannot be sufficiently decreased. On the contrary, when it is more than50 parts by weight, the synthesis cost of the oxidizing catalyst becomeshigh.

The oxidizing catalyst includes 10 to 70 parts by weight of the solidacid based on 100 parts by weight of the oxidizing catalyst. Accordingto one embodiment, the oxidizing catalyst includes 20 to 60 parts byweight of the solid acid based on 100 parts by weight of the oxidizingcatalyst. When the amount of the solid acid is less than 10 parts byweight, the solid acid effect is not sufficient, while when it is morethan 70 parts by weight, oxidizing catalyst activity may be deterioratedand thus the starting temperature of the fuel oxidation by the oxidizingcatalyst cannot be sufficiently decreased.

The oxidizing catalyst may further include a carrier supporting theplatinum-based metal and the solid acid. The carrier may be selectedfrom the group consisting of Al₂O₃, TiO₂, SiO₂, ZrO₂, MgO, andcombinations thereof. According to one embodiment, a granule type ofAl₂O₃ may be appropriate.

When the oxidizing catalyst further includes the carrier, the oxidizingcatalyst includes less than 89.5 parts by weight of the carrier based on100 parts by weight of an oxidizing catalyst. According to oneembodiment, the oxidizing catalyst includes 35 to 80 parts by weight ofthe carrier based on 100 parts by weight of an oxidizing catalyst. Whenthe amount of the carrier is more than or equal to 89.5 parts by weight,the amount of the solid acid is also decreased resulting in reduction ofacid sites, and the amount of Pt is decreased resulting in reduction ofoxidizing catalyst activity. Therefore, the starting temperature of thefuel oxidation by the oxidizing catalyst cannot be sufficientlydecreased.

Exemplary methods of producing the oxidizing catalyst are described asfollows.

The oxidizing catalyst can be synthesized as follows. A strong acid ionis impregnated into an inorganic oxide and the resulting product isfired to prepare a solid acid. A platinum-based metal is impregnatedinto the solid acid, and the resulting product is fired to prepare anoxidizing catalyst.

For impregnating the strong acid ion into the inorganic oxide, theresulting inorganic oxide and a strong acid ion-containing compound areadded to a solvent.

The inorganic oxide includes an oxide of an element selected from thegroup consisting of Zr, Al, Ti, Si, Mg, Zn, and combinations thereof.The strong acid ion-containing compound includes at least one selectedfrom the group consisting of sulfuric acid, ammonium sulfate, sulfurousacid, ammonium sulfite, thionyl chloride, dimethyl sulfuric acid,phosphoric acid, ammonium phosphate, and combinations thereof. Thesolvent includes at least one selected from the group consisting ofwater, ethanol, isopropanol, acetone, methyl ethyl ketone, methylisobutyl ketone, and combinations thereof.

The firing temperature to prepare the solid acid (i.e., the temperaturefor firing the strong acid impregnated into the inorganic oxidesupported on the carrier) is varied depending on the firing time.According to one embodiment, the temperature may range from 400 to 900°C. According to another embodiment, the temperature may range from 550to 750° C. When the firing temperature is less than 400° C, calcinationsare not completely implemented, while when it is more than 900° C.,calcinations may be finished before the firing time is complete, andthus process time and cost may be wasted.

The firing time to prepare the solid acid is varied depending on thefiring temperature. According to one embodiment, the firing time maygenerally range from 1 to 5 hours. According to another embodiment, thefiring time may range from 2 to 4 hours. When the firing time is lessthan 1 hour, calcinations are not completely implemented, while when itis more than 5 hours, calcinations may be finished before the firingtime is complete, and thus process time and cost may be wasted.

For impregnating the platinum-based metal into the solid acid, the aboveprepared solid acid and a platinum-based metal-containing precursor areadded to a solvent.

The platinum-based metal-containing precursor is at least one selectedfrom the group consisting of H₂PtCl₆, Pt(C₅H₇O₂)₂, H₆Cl₂N₂Pt, PtCl₂,PtBr₂, PdCl₂, Pd(C₂H₃O₂)₂, Pd(C₅H₇O₂)₂, RuCl₃, Ru(C₅H₇O₂)₃, (NH₄)₂RuCl₆,(NH₄)₃RhCl₆, [Rh(CH₃COO)₂]₂,Rh(H₂O) (NO₃)₃, hydrates thereof, andcombinations thereof. The solvent includes at least one selected fromthe group consisting of water, ethanol, isopropanol, acetone, methylethyl ketone, methyl isobutyl ketone, and combinations thereof.

The firing temperature to prepare the oxidizing catalyst (i.e., thetemperature for firing the platinum-based metal impregnated into thesolid acid) is varied depending on a firing time. According to oneembodiment, the temperature may range from 400 to 900° C. According toanother embodiment, the temperature may range from 550 to 750° C. Whenthe firing temperature is less than 400° C., calcinations are notcompletely implemented, while when it is more than 900° C., calcinationsmay be finished before the firing time is complete, and thus processtime and cost may be wasted and a pore structure of the resultingoxidizing catalyst may be damaged.

The firing time is varied depending on the firing temperature. Accordingto one embodiment, the firing time may generally range from 1 to 5hours. According to another embodiment, the firing time may range from 2to 4 hours. When the firing time is less than 1 hour, calcinations arenot completely implemented, while when it is more than 5 hours,calcinations may be finished before the firing time is complete, andthus a process time and cost may be wasted and a pore structure of theresulting oxidizing catalyst may be damaged.

In the case when the oxidizing catalyst further includes a carriersupporting the platinum-based metal and a solid acid, the oxidizingcatalyst may be prepared as follows. An inorganic oxide precursor and acarrier are mixed and fired to prepare an inorganic oxide supported onthe carrier. A strong acid is impregnated into the inorganic oxidesupported on the carrier and the resulting product is fired to prepare asolid acid. A platinum-based metal is impregnated into the preparedsolid acid and then fired to prepare an oxidizing catalyst which furtherincludes the carrier.

The inorganic oxide precursor may be any one that can be fired toproduce an inorganic oxide. Examples of the inorganic oxide precursorinclude, but are not limited to, at least one selected from the groupconsisting of nitrate, chlorides, bromides, methoxide, ethoxide,propoxide, butoxide, and combinations thereof, which includes an elementselected from the group consisting of Zr, Al, Ti, Si, Mg, Zn, andcombinations thereof.

The carrier may be selected from the group consisting of Al₂O₃, TiO₂,SiO₂, ZrO₂, MgO, and combinations thereof. According to one embodiment,a granule type of Al₂O₃ may be appropriate.

The firing temperature to prepare the inorganic oxide supported on thecarrier is varied depending on the firing time. According to oneembodiment, the temperature may range from 100 to 500° C. According toanother embodiment, the temperature may range from 200 to 400° C. Whenthe firing temperature is less than 100° C., calcinations are notcompletely implemented, while when it is more than 500° C., calcinationsmay be finished before the firing time is complete, and thus processtime and cost may be wasted.

The firing time to prepare the inorganic oxide supported on the carrieris varied depending on the firing temperature. According to oneembodiment, the firing time may generally range from 1 to 5 hours.According to another embodiment, the firing time may range from 2 to 4hours. When the firing time is less than 1 hour, calcinations are notcompletely implemented, while when it is more than 5 hours, calcinationsmay be finished before the firing time is complete, and thus processtime and cost may be wasted.

The firing temperatures to prepare the solid acid (i.e., the temperaturefor firing the strong acid impregnated into the inorganic oxidesupported on the carrier) and the oxidizing catalyst (i.e., thetemperature for firing the platinum-based metal impregnated into thesolid acid) are varied depending on a firing time. According to oneembodiment, the temperature may range from 400 to 900° C. According toanother embodiment, the temperature may range from 550 to 750° C. Whenthe firing temperature is less than 400° C., calcinations are notcompletely implemented, while when it is more than 900° C., calcinationsmay be finished before a firing time is complete, and thus process timeand cost may be wasted and a pore structure of the resulting oxidizingcatalyst may be damaged.

The firing time is varied depending on the firing temperature. Accordingto one embodiment, the firing time may generally range from 1 to 5hours. According to another embodiment, the firing time may range from 2to 4 hours. When the firing time is less than 1 hour, calcinations arenot completely implemented, while when it is more than 5 hours,calcinations may be finished before the firing time is complete, andthus process time and cost may be wasted and a pore structure of theresulting oxidizing catalyst may be damaged.

According to another embodiment of the present invention, a reformer fora fuel cell system is provided, which includes a heating source forgenerating heat by reaction of a fuel and an oxidant using an oxidizingcatalyst, and a reforming reaction part for generating hydrogen by areforming catalyst reaction. The heating source includes a firstreacting region that includes a platinum-based catalyst including asolid acid which includes a strong acid ion and an inorganic oxide, anda platinum-based metal, and a second reacting region including anon-platinum-based catalyst.

Since the heating source of a reformer includes a platinum-basedcatalyst, a fuel oxidizing catalyst reaction starts at a lowtemperature. In addition, since it includes a platinum-based catalyst ina smaller amount than a conventional heating source, it can decrease amanufacturing cost.

The first and second reacting regions may be sequentially disposed.

The fuel and oxidant may be sequentially supplied to the first reactingregion and then to the second reacting region.

The fuel and oxidant are supplied to the first reacting region andundergo a fuel oxidizing catalyst reaction due to a platinum-basedcatalyst at a low temperature. The fuel oxidizing catalyst reaction inthe first reacting region produces heat, which causes a fuel oxidizingcatalyst reaction in the second reacting region. Resultantly, the fueloxidizing catalyst reaction proceeds in the second reacting regionincluding a non-platinum-based catalyst at a low temperature.

The platinum-based catalyst and the non-platinum-based catalyst may beincluded in a volume ratio of 1:1 to 1:5. In one embodiment, theplatinum-based catalyst and the non-platinum-based catalyst may beincluded in a volume ratio of 1:1 to 1:4. However, in anotherembodiment, the platinum-based catalyst and the non-platinum-basedcatalyst may be included in a volume ratio of 1:2 and 1:3. Since theplatinum-based catalyst has excellent activity for a fuel oxidizingcatalyst reaction but is expensive, it has no particular limit to itsamount but should be included in a small amount to decrease cost. Theplatinum-based catalyst in the first reacting region plays a role ofinitiating a fuel oxidizing catalyst reaction at a low temperaturewithin the aforementioned volume ratio range.

The strong acid ion, the solid acid, the platinum-based metal, and theinorganic oxide are the same as in the reformer of a fuel cell systemaccording to an embodiment as described above.

The platinum-based catalyst may include more than 0.5 parts by weightand less than or equal to 50 parts by weight of the platinum-based metaland 10 to 70 parts by weight of the solid acid. In one embodiment, theplatinum-based catalyst may include the platinum-based metal and thesolid acid in a weight ratio of 1 to 5:20 to 60. In another embodiment,the platinum-based catalyst may include the platinum-based metal andsolid acid in a weight ratio of 1:10, 1:30, 1:50, 1:70, 10:10, 10:30,10:50, 10:70, 30:10, 30:30, 30:50, 30:70, 50:10, 50:30, 50:50, or 50:70.

When the weight ratio of the platinum-based metal is less than 0.5, thecatalyst may have reduced activity and thereby cannot sufficientlydecrease the starting temperature of a fuel oxidizing catalyst, whilewhen it is more than 50, the cost for manufacturing the catalyst mayincrease.

When the weight ratio of the solid acid is included in an amount of lessthan 10, a platinum-based catalyst may not have the sufficient effect ofthe solid acid, while when included in an amount of more than 70, aplatinum-based catalyst may have decreased activity and cannotsufficiently decrease the starting temperature of the fuel oxidizingcatalyst reaction

The platinum-based catalyst may further include a carrier supporting theplatinum-based metal and solid acid. The carrier may be selected fromthe group consisting of Al₂O₃, TiO₂, SiO₂, ZrO₂, MgO, and combinationsthereof. In one embodiment, a granule type of Al₂O₃ may be appropriatefor the carrier.

When the platinum-based catalyst may further include a carrier, thecarrier may be included in an amount of less than 89.5 parts by weightof the carrier based on 100 parts by weight of a platinum-basedcatalyst. In one embodiment, the carrier may be included in an amount of35 to 80 parts by weight based on 100 parts by weight of aplatinum-based catalyst. In one embodiment, the carrier may be includedin an amount of 80, 70, 60, 50, 40, 30, 20,10, or 1 part by weight basedon 100 parts by weight of a platinum-based catalyst. When the carrier isincluded in an amount of more than or equal to 89.5 parts by weightbased on 100 parts by weight of a platinum-based catalyst, the solidacid is less included, decreasing the numbers of acid sites. Inaddition, a platinum-based metal is less included, resultantlydecreasing the platinum-based catalyst activity and thereby notsufficiently lowering the starting temperature of the fuel oxidizingcatalyst.

For the non-platinum-based catalyst, any fuel oxidizing catalyst for aheating source without a platinum-based metal can be used. Thenon-platinum-based catalyst may include a metal oxide including CeO₂, MO(wherein M is a transition element), and CuO.

The metal oxide including CeO₂, MO, and CuO stores an oxidant. In otherwords, the metal oxide supplies an oxidant during the oxidizing catalystreaction of a fuel. Since the metal oxide abundantly includes anoxidant, it can speed up the reaction rate of the fuel and oxidant andcause a fuel oxidizing catalyst reaction at a low temperature.

The non-platinum-based catalyst may include 10 to 30 parts by weight ofCeO₂ based on the weight of the non-platinum-based catalyst. In oneembodiment, the non-platinum-based catalyst may include 15 to 25 partsby weight of CeO₂ based on the weight of the non-platinum-basedcatalyst.

In another embodiment, the non-platinum-based catalyst may include 10,15, 20, 25, or 30 parts by weight of CeO₂ based on the weight of thenon-platinum-based catalyst.

When the CeO₂ is included in an amount of less than 10 parts by weight,an oxidant may have too low a diffusion concentration. On the otherhand, when it is included in an amount of 30 parts by weight, thenon-platinum-based catalyst may have sharply deteriorated pore structureand thermal stability.

The non-platinum-based catalyst may include 0.1 to 5 parts by weight ofMO based on the weight of the non-platinum-based catalyst. In oneembodiment, it may include 3.5 to 4.5 parts by weight of CeO₂ based onthe weight of the non-platinum-based catalyst.

In another embodiment, the MO may be included in an amount of 0.1, 0.5,1, 2, 3, 4, or 5 parts by weight. When the MO is included in an amountof less than 0.1 parts by weight, the MO may have little effect. On thecontrary, when it is included in an amount of more than 5 parts byweight, a non-platinum-based catalyst may have rather deterioratedactivity.

The M of the MO is a transition element selected from the groupconsisting of Ni, Co, Fe, and combinations thereof.

In one embodiment, the non-platinum-based catalyst includes 1 to 10parts by weight of CuO, but in another embodiment, it includes 2.5 to 5parts by weight of CuO. In another embodiment, the CuO may be includedin an amount of 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts by weight. Whenthe CuO is included in an amount of less than 1 part by weight, thenon-platinum-based catalyst may have too low oxygen storage capability,while when the CuO is included in an amount of more than 10 parts byweight, it may have deteriorated activity.

The metal oxide including CeO₂, MO, and CuO may be supported on acarrier selected from the group consisting of Al₂O₃, TiO₂, SiO₂,cordierite, and combinations thereof. In one embodiment, Al₂O₃ isappropriate for the carrier for supporting the metal oxide.

The non-platinum-based catalyst may include 55 to 88.9 parts by weightof the carrier based on the weight of the non-platinum-based catalyst.In one embodiment, the carrier may be included in an amount of 55, 60,65, 70, 75, 80, 85, or 88.9 parts by weight. When the amount of thecarrier is less than 55 parts by weight, the mechanical strength of thenon-platinum-based catalyst is not sufficient and its porosity becomessmaller, while when it is more than 88.9 parts by weight, the relativeamount of the metal oxide lessens resulting in activity decrease of thenon-platinum-based catalyst.

In addition, the metal oxide may be a solid solution of CeO₂, MO, andCuO. When the metal oxide is a solid solution, the CeO₂, MO, and CuO areuniformly dispersed at a molecular level. Therefore, the metal oxide canimprove capability of storing an oxidant, and resultantly, supply moreoxidant to a fuel.

The non-platinum-based catalyst including the CeO₂, MO (wherein M is atransition element), and CuO may further include ZrO₂. The ZrO₂ improvesstability of the non-platinum-based catalyst at a high temperature. TheZrO₂ helps a surface active material melted into the catalyst at a hightemperature of 800° C. or more, and thus prevents collapse of activesites of the catalyst.

When the non-platinum-based catalyst further includes ZrO₂, thenon-platinum-based catalyst includes 5 to 20 parts by weight of ZrO₂, 5to 20 parts by weight of CeO₂, 0.1 to 5 parts by weight of MO, and 1 to10 parts by weight of CuO.

In another embodiment, the ZrO₂ may be included in an amount of 5, 10,15, or 20 parts by weight. When the amount of ZrO₂ is less than 5 partsby weight, the non-platinum-based catalyst may not have sufficientstability improvement at a high temperature, while when it is more than20 parts by weight, the non-platinum-based catalyst may havedeteriorated activity.

According to another embodiment of the present invention, provided is afuel cell system that includes the above reformer, at least oneelectricity generating element for generating electrical energy by anelectrochemical reaction of hydrogen and an oxidant, a fuel supplier forsupplying a fuel to the reformer, and an oxidant supplier for supplyingan oxidant to the reformer and the electricity generating element.

An embodiment of the present invention will hereinafter be described indetail with reference to the accompanying drawings. However, the presentinvention may have various modifications and equivalent arrangements andit is to be understood that the invention is not limited to thedescribed embodiments.

FIG. 1 is a schematic view showing the whole structure of a fuel cellsystem according to one embodiment of the present invention, and FIG. 2is an exploded perspective view showing the stack structure illustratedin FIG. 1.

Referring to the drawings, a fuel cell system 100 is a polymerelectrolyte membrane fuel cell (PEMFC) where a hydrogen-containing fuelis reformed to generate hydrogen, and then electrical energy isgenerated by an electrochemical reaction of the hydrogen and an oxidant.

In the fuel cell system 100, the oxidant includes a gas that reacts withhydrogen, for example oxygen or air containing oxygen stored in aseparate storing space.

The fuel cell system 100 includes electricity generating elements 11that generate electrical energy through an electrochemical reaction of areformed gas supplied from a reformer 30 and an oxidant, a fuel supplier50 for supplying a fuel to the reformer 30, the reformer 30 thatgenerates hydrogen from a fuel and supplies the hydrogen to theelectricity generating element 11, and an oxidant supplier 70 forsupplying the oxidant to the reformer 30 and the electricity generatingelements 11. The electricity generating elements 11 are stacked to forma stack 10.

Such a fuel cell system 100 can be a power source for supplying apredetermined electrical energy to any load such as a portableelectronic device, including a laptop computer and a PDA, or a mobiletelecommunication device.

The reformer 30 generates hydrogen from the hydrogen-included fuel by achemical catalyst reaction, for example a steam reforming reaction, apartial oxidation, or an autothermal reaction, and supplies thegenerated hydrogen to the stack 10. The reformer 30 is connected withthe stack 10 and the fuel supplier 50 via a pipe line and so on.

The reformer 30 includes the heating source 35 generating thepredetermined heat required for the reforming catalyst reaction of thefuel by the oxidation catalyst reaction between the fuel and the oxidantrespectively supplied from the fuel supplier 50 and the oxidant supplier70, and a reforming reaction part 39 absorbing the heat generated fromthe heating source 35 to generate hydrogen from the fuel via thereforming catalyst reaction of the fuel supplied from the fuel supplier50. The reformer further includes a carbon monoxide reducing part wherecarbon monoxide is optionally oxidized.

The heating source 35 of the reformer 30 and the reforming reaction part39 may be independently equipped and connected to each other via acommon connection element. Alternatively, they may be incorporated in adouble pipeline where the heating source 35 is disposed inside and thereforming reaction part 39 is disposed outside.

The heating source 35 generates heat through a reaction of a fuel and anoxidant by an oxidizing catalyst that includes a solid acid whichincludes a strong acid ion and an inorganic oxide, and a platinum-basedmetal.

The reforming reaction part 39 includes a reactor body, and a reformingcatalyst in the reactor body. The reactor body can be made in variousshapes. According to one embodiment, a container-type reactor bodyhaving a predetermined inside space may be appropriate.

The reforming catalyst promotes a reforming reaction of a fuel byabsorbing heat from the heating source 35 and includes at least onecatalyst selected from the group consisting of nickel (Ni), platinum(Pt), ruthenium (Ru), silver (Au), palladium (Pd), copper (Cu), zinc(Zn), a copper-zinc alloy (Cu—Zn), and combinations thereof, that issupported on a carrier selected from the group consisting of alumina(Al₂O₃), silica (SiO₂), titania (TiO₂), and combinations thereof in apellet shape.

When the reactor body is composed of a reaction substrate, the reformingcatalyst is in a channel of the reaction substrate. Alternatively, whenthe reactor body is composed of a container, a pellet or honey-comb typereforming catalyst is filled inside the reactor body.

The fuel supplier 50 for supplying the fuel to the reformer 30 includesa fuel tank 51 containing the fuel to be supplied to the reformer 30 anda fuel pump 53 connecting with the fuel tank 51 and supplying the fuelfrom the fuel tank 51. The fuel tank 51 is connected with the heatingsource 35 of the reformer 30 and the reforming reaction part 39 via pipelines.

The oxidant supplier 70 includes an air pump 71 inhaling an oxidant witha predetermined pumping force, and supplying the oxidant to theelectricity generating elements 11 of the stack 10 and the heatingsource 35. According to the present embodiment shown in the drawing, theoxidant supplier 70 is illustrated to supply the oxidant to the stack 10and the heating source 35 via a single air pump 71, but it is notlimited thereto. It may include a pair of oxidant pumps mounted to thestack 10 and the heating source 35 respectively.

Upon driving the system 100 according to one embodiment of the presentinvention, hydrogen generated from the reformer 30 is supplied to theelectricity generating elements 11 and the oxidant is supplied to theelectricity generating elements 11, and thereby the electrochemicalreaction occurs by the oxidation reaction of the hydrogen and thereduction reaction of the oxidant to generate electrical energy having apredetermined power output, as well as water and heat.

Furthermore, the fuel cell system 100 may include a common control unit(not shown) mounted separately that substantially controls the overalloperation of the system, for example, operations of the fuel supplier 50and the oxidant supplier 70.

As shown in FIG. 2, the stack 10 is composed of stacked electricitygenerating elements 11. Each electricity generating element 11 includesa membrane-electrode assembly (MEA) 12 and separators (or bipolarplates) 16 disposed at both sides of the MEA to constitute a fuel cellas a minimum unit.

The membrane-electrode assembly 12 includes an anode and a cathoderespectively having active areas for the electrochemical reaction ofhydrogen and an oxidant, and an electrolyte membrane interposed betweenthe anode and the cathode.

At the anode, hydrogen is oxidized to produce protons and electrons, andat the cathode, the protons react with an oxidant to generate heat andmoisture. The electrolyte membrane functions as an ion exchanger fortransferring the protons generated at the anode to the cathode. Theseparators 16 supply a fuel and an oxidant to the membrane-electrodeassemblies 12, and also work as conductors for serially coupling theanodes and the cathodes in the membrane-electrode assemblies 12.

As such a stack 10 may be provided as in a stack of a general polymerelectrolyte type fuel cell, a detailed description thereof is omittedfrom this specification.

The following examples illustrate the present invention in more detail.However, it is understood that the present invention is not limited bythese examples.

Preparation of an Oxidizing Catalyst

EXAMPLE 1

33.03 g of ZrO(NO₃)₂.6H₂O and 20 g of a granule type of Al₂O₃ were addedto 300 ml of water, and the resulting product was fired at 300° C. for 1hour to prepare ZrO₂ supported on Al₂O₃. 0.981 g of H₂SO₄ was added to30 ml of water to prepare an impregnation solution. The solution wasimpregnated into 25g of ZrO₂ supported on Al₂O₃, and the product wasfired at 650° C. for 3 hours to prepare solid acid ZrO₂—SO₄ ²⁻ supportedon Al₂O₃.

3 g of H₂PtCl₆.6H₂O was added to 10 ml of water to prepare a PtPrecursor solution. 2 ml of the Pt precursor solution was added to 18 mlof water to prepare an impregnation solution. The impregnation solutionwas impregnated into the 25g of ZrO₂—SO₄ ²⁻, and then the resultingproduct was fired at 650° C. for 1.5 hours to prepare an oxidizingcatalyst. The oxidizing catalyst included ZrO₂—SO₄ ² ⁻ and Pt, withAl₂O₃ supporting the Pt and ZrO₂—SO₄ ²⁻. The oxidizing catalyst included1 part by weight of Pt, 60 parts by weight of the solid acid, and 39parts by weight of Al₂O₃ based on 100 parts by weight of the oxidizingcatalyst.

EXAMPLE 2

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 1 part by weightof Pt, 40 parts by weight of the solid acid, and 59 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 3

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 1 part by weightof Pt, 20 parts by weight of the solid acid, and 79 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 4

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 2 parts by weightof Pt, 60 parts by weight of the solid acid, and 38 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 5

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 2 parts by weightof Pt, 40 parts by weight of the solid acid, and 58 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 6

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 2 parts by weightof Pt, 20 parts by weight of the solid acid, and 78 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 7

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 3 parts by weightof Pt, 60 parts by weight of the solid acid, and 37 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 8

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 3 parts by weightof Pt, 40 parts by weight of the solid acid, and 57 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 9

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 3 parts by weightof Pt, 20 parts by weight of the solid acid, and 77 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 10

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 4 parts by weightof Pt, 60 parts by weight of the solid acid, and 36 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 11

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 4 parts by weightof Pt, 40 parts by weight of the solid acid, and 56 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 12

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 4 parts by weightof Pt, 20 parts by weight of the solid acid, and 76 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 13

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 5 parts by weightof Pt, 60 parts by weight of the solid acid, and 35 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 14

The oxidizing catalyst was prepared according to the same method as inExample 1, except that the oxidizing catalyst included 5 parts by weightof Pt, 40 parts by weight of the solid acid, and 55 parts by weight ofAl₂O₃ based on 100 parts by weight of the oxidizing catalyst.

EXAMPLE 15

11.019 g of ZrO(NO₃)₂.6H₂O and 20 g of Al₂O₃ were added to 100 ml ofwater, and the resulting product was fired at 300° C. for 1 hour toprepare ZrO₂ supported on Al₂O₃. 0.981 g of H₂SO₄ was added to 30 ml ofwater to prepare a solution. The solution was impregnated into 20 g ofZrO₂ supported on Al₂O₃, and the product was fired at 650° C. for 3hours to prepare solid acid ZrO₂—SO₄ ²⁻.

3 g of H₂PtCl₆.6H₂O was added to 10 ml of water to prepare a Ptprecursor solution. 2.5 ml of the Pt precursor solution was added to 0.5ml of water to prepare an impregnation solution. The impregnationsolution was impregnated into the 6 g of ZrO₂—SO₄ ²⁻ and then theresulting product was fired at 650° C. for 1.5 hours to prepare anoxidizing catalyst. The oxidizing catalyst included ZrO₂—SO₄ ²⁻ and Pt,with Al₂O₃ supporting the Pt and ZrO₂—SO₄ ²⁻. The oxidizing catalystincluded 5 parts by weight of Pt, 20 parts by weight of the solid acid,and 75 parts by weight of Al₂O₃ based on 100 parts by weight of theoxidizing catalyst.

Preparation of a Heating Source and Measurement of a Reaction StartingTemperature

Two tube reactors were fabricated and one reactor was charged with 9 mlof the oxidizing catalyst prepared from Example 1 and the other reactorwas charged with 8 ml of the oxidizing catalyst prepared from Example 15to provide a heating source for a reformer. Fuels, including 35 volume %of isobutane, 50 volume % of n-butane, and 15 volume % of C₃H₈, weresupplied to each heating source at 279.1 ml/min and air was supplied at2000 ml/min. Further, the heating source was maintained to have aninside temperature at 90° C. by a heater.

The inside temperature of each heating source was monitored. The resultsof the heating source charged with the oxidizing catalyst according toExample 1 are shown in FIG. 3, and the results of the heating sourcecharged with the oxidizing catalyst according to Example 15 are shown inFIG. 4. As shown in FIG. 3 and FIG. 4, it was confirmed that theoxidizing catalyst reaction was started even with the inside temperatureof the heating source at 90° C.

This test was repeated with the oxidizing catalysts prepared fromExamples 2 to 14, and it was confirmed that the oxidizing catalystreaction was started even at 90° C.

COMPARATIVE EXAMPLES 1 TO 15

Comparative Examples 1 to 8 included oxidizing catalysts disclosed inTörncrona's papers (Low temperature catalytic activity of cobalt oxideand ceria promoted Pt and Pd: Influence of pretreatment and gascomposition, applied Catalysis B: Environmental, Volume 14, Issues 1-2,5 Dec. 1997, Pages 131-145, A. Törncrona et al., which is incorporatedherein by reference). The temperatures for starting the oxidationreaction of the oxidizing catalysts and the fuel are shown in Table 1.

The oxidizing catalyst of Comparative Example 9 is the catalystdisclosed in U.S. Pat. No. 5,345,011, which is incorporated herein byreference. The starting temperature of the oxidation reaction of thefuel by the oxidizing catalyst is shown in Table 1.

The oxidizing catalysts of Comparative Examples 10 to 13 are thecatalysts disclosed in U.S. Pat. No. 5,139,994, which is incorporatedherein by reference. The starting temperatures of the oxidation reactionof the fuel by the oxidizing catalysts are shown in Table 1.

The oxidizing catalyst of Comparative Example 14 is the catalystdisclosed in U.S. Pat. No. 6,187,709, which is incorporated herein byreference. The starting temperature of the oxidation reaction of thefuel by the oxidizing catalyst is shown in Table 1.

The oxidizing catalyst of Comparative Example 15 is the catalystdisclosed in U.S. Pat. No. 6,086,835, which is incorporated herein byreference. The starting temperature of the oxidation reaction of thefuel by the oxidizing catalyst is shown in Table 1.

TABLE 1 Reaction starting temperature Oxidizing catalyst Fuel (° C.)Comp. Ex. 1 1 wt % Pt/Al₂O₃ propane 300 Monolith carrier Comp. Ex. 2 0.5wt % Pd/Al₂O₃ propane 245 Monolith carrier Comp. Ex. 3 1 wt % Pt/20 wt %CeO₂/Al₂O₃ propane 247 Monolith carrier Comp. Ex. 4 0.5 wt % Pd/20 wt %CeO₂/Al₂O₃ propane 256 Monolith carrier Comp. Ex. 5 1 wt % Pt/20 wt %Co₂O₃/Al₂O₃ propane 237 Monolith carrier Comp. Ex. 6 0.5 wt % Pd/20 wt %propane 246 Monolith Co₂O₃/Al₂O₃ carrier Comp. Ex. 7 20 wt % CeO₂/Al₂O₃propane 237 Monolith carrier Comp. Ex. 8 20 wt % Co₂O₃/Al₂O₃ propane 364Monolith carrier Comp. Ex. 9 13 wt % Mn supported on methane 200 to 450Space crystalline aluminophosphate velocity 200 structural framework to2000 h⁻¹ Comp. Ex. 10 platinum/alumina catalyst propane 262 — Comp. Ex.11 TiO₂/Pt/Al₂O₃ propane 297 — Comp. Ex. 12 platinum/alumina catalystethane 523 Fuel including 20 volume % of SO₂ Comp. Ex. 13 TiO₂/Pt/Al₂O₃ethane 500 Fuel including 20 volume % of SO₂ Comp. Ex. 14palladium-based catalyst 450 — Comp. Ex. 15 0.5 wt % gold, 9.5 wt %cobalt, 80 wt % 300 Space zirconium oxide/cerium velocity oxide and 10wt % titanium 60000 h⁻¹ dioxide

As shown by Table 1, Examples 1 to 15 showed a lower startingtemperature of the oxidizing catalyst reaction than that of ComparativeExamples 1 to 15.

Preparation of Oxidizing Catalyst

EXAMPLE 16 Preparation of a Platinum-Based Catalyst

33.03 g of ZrO(NO₃)₂.6H₂O and 20 g of Al₂O₃ were added to 300 ml ofwater. The prepared product was fired at 300° C. for 1 hour, preparingZrO₂ supported on Al₂O₃. Then, 0.981 g of H₂SO₄ was added to 30 ml ofwater, preparing an impregnation solution, and 25 g of the ZrO₂supported on Al₂O₃ was impregnated therewith. The resulting product wasfired at 650° C. for 3 hours, preparing solid acid ZrO₂—SO₄ ²⁻.

3 g of H₂PtCI₆.6H₂O was added to 10 ml of water, preparing a Ptprecursor solution. 2 ml of the prepared Pt precursor solution was addedto 18 ml of water, preparing an impregnation solution. 25 g of theZrO₂—SO₄ ²⁻ was impregnated with the impregnation solution. Theresulting product was fired at 650° C. for 1.5 hours, preparing anoxidizing catalyst. The oxidizing catalyst included ZrO₂—SO₄ ²⁻ and Pt,and Al₂O₃ supporting them. The oxidizing catalyst included 1 part byweight of Pt, 60 parts by weight of solid acid, and 39 parts by weightof Al₂O₃.

EXAMPLE 17 Prepartion of a Non-Platinum-Based Catalyst

162.34 g of Cu(NO₃)₂.3H₂O was dissolved in 500 ml of water. Next, 10.60g of Ce(NO₃)₃.6H₂O and 4.124 g of Ni(NO₃)₂.6H₂O were dissolved in 7.4 mlof the prepared Cu aqueous solution, preparing a mixed solution. Then,14.84 g of Al₂O₃ was added to the mixed solution. The resulting solutionincluding Al₂O₃ was stirred and heated at 100° C. to evaporate water,preparing 190.068 g of a metal oxide. The metal oxide was calcinated at500° C. for 1 hour.

The prepared fuel oxidizing catalyst included 20 parts by weight ofCeO₂, 4 parts by weight of NiO, 4 parts by weight of CuO, and 72 partsby weight of Al₂O₃.

Preparation of a Heating Source and Its Performance Measurement

REFERENCE EXAMPLE 1

Stainless steal tube reactors (GMS 1000®, Sunyoung Sys-Tech Company) wascharged with 23 ml of the fuel oxidizing catalyst according to Example16 to fabricate a heating source.

Fuels, including 35 volume % of isobutane, 50 volume % of n-butane, and15 volume % of C₃H₈, were supplied to the heating source, so that butanemight be supplied at 1,160 ml/min, and air was supplied at 10,000ml/min. A space velocity was set to be 26,932 h⁻¹.

The reactor temperatures of the fuel inlet, the fuel outlet, and thecenter between the inlet and outlet were measured by using threethermocouples. The measurement results are shown in FIG. 5.

EXAMPLE 18

A heating source was prepared according to the same method as inReference Example 1, except for charging 5 ml of the non-platinum-basedcatalyst according to Example 17 at the fuel inlet portion of thereactor, and the other portion of the reactor is charged with the fueloxidizing catalyst according to Example 16.

Fuels, including 35 volume % of isobutane, 50 volume % of n-butane, and15 volume % of C₃H₈, were supplied to the heating source, so that butanemight be supplied at 1160 ml/min, and air was supplied at 10,000 ml/min.A space velocity was set to be 123,885 h⁻¹.

The reactor temperatures of the fuel inlet, the fuel outlet, and thecenter between the inlet and outlet were measured by using threethermocouples. The measurement results are shown in FIG. 6.

EXAMPLE 19

A heating source was prepared according to the same method as inReference Example 1, except for charging the fuel inlet portion of thereactor with 5 ml of the fuel oxidizing catalyst according to Example 16and the other part of the reactor was charged with 18 ml of the fuelnon-platinum-based catalyst according to Example 17.

Fuels, including 35 volume % of isobutane, 50 volume % of n-butane, and15 volume % of C₃H₈, were supplied to the heating source, so that butanemight be supplied at 1160 ml/min, and air was supplied at 10,000 ml/min.A space velocity was set to be 26,932 h⁻¹.

The reactor temperatures of the fuel inlet, fuel outlet, and centerbetween the inlet and outlet were measured by using three thermocouples.The measurement results are shown in FIG. 7.

Referring to FIG. 5, when a heating source was fully charged with aplatinum-based catalyst, a fuel oxidizing catalyst reaction was found tobe stable despite a space velocity of 26,396 h⁻¹.

Referring to FIG. 6, a heating source was partly charged with aplatinum-based catalyst, and a main fuel oxidizing catalyst reaction wasfound to occur at two different areas which show the higher temperaturesin a reactor. In other words, a fuel oxidizing catalyst reactionoccurred around the inlet of a reactor charged with a platinum-basedmetal in the beginning, but proceeded to the middle of the reactor andaround the outlet not charged with a catalyst as time passed.

Accordingly, a platinum-based catalyst turned out to lower an initiativetemperature even when it was partly charged at the side of the inlet ofthe reactor.

Referring to FIG. 7, a fuel oxidizing catalyst started reacting at a lowtemperature and stably proceeded as time passes. Accordingly, even asmall amount of a platinum-based catalyst in the reactor can start areaction at a low temperature. Even when the remaining amount of theplatinum-based catalyst can be replaced with a non-platinum-basedcatalyst, the platinum-based catalyst can stabilize a fuel oxidizingcatalyst reaction.

The reformer for a fuel cell system can start a fuel oxidation catalystreaction, and includes a heating source having a simplified structure.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A reformer for a fuel cell system, comprising: a heating sourcecomprising an oxidizing catalyst for generating heat by a reaction of afuel and an oxidant using the oxidizing catalyst, the oxidizing catalystcomprising: a solid acid comprised of an inorganic oxide and a strongacid ion bound to the inorganic oxide; a platinum-based metal supportedon the solid acid; and a carrier supporting the solid acid and theplatinum-based metal; and a reforming reaction part for generatinghydrogen by a reforming catalyst reaction.
 2. The reformer of claim 1,wherein the platinum-based metal is selected from the group consistingof Pt, Pd, Ru, Rh, and combinations thereof.
 3. The reformer of claim 1,wherein the inorganic oxide comprises an oxide of an element selectedfrom the group consisting of Zr, Al, Ti, Si, Mg, Zn, and combinationsthereof.
 4. The reformer of claim 1, wherein the strong acid ioncomprises at least one selected from the group consisting of sulfateion, phosphate ion, and combinations thereof.
 5. The reformer of claim1, wherein the oxidizing catalyst comprises more than 0.5 parts byweight and less than or equal to 50 parts by weight of theplatinum-based metal based on 100 parts by weight of the oxidizingcatalyst, and 10 to 70 parts by weight of the solid acid based on 100parts by weight of the oxidizing catalyst.
 6. The reformer of claim 1,wherein the carrier is selected from the group consisting of Al₂O₃,TiO₂, SiO₂, ZrO₂, MgO, and combinations thereof.
 7. The reformer ofclaim 1, wherein the oxidizing catalyst comprises less than 89.5 partsby weight of the carrier based on 100 parts by weight of an oxidizingcatalyst.
 8. The reformer of claim 1, wherein the oxidizing catalystcomprises more than 0.5 parts by weight and less than or equal to 50parts by weight of the platinum-based metal of Pt, 10 to 70 parts byweight of the solid acid of ZrO₂—SO₄ ²⁻, and less than 89.5 parts byweight of the carrier of Al₂O₃, based on 100 parts by weight of theoxidizing catalyst.
 9. A reformer for a fuel cell system, comprising: aheating source for generating heat by a reaction of a fuel and anoxidant using an oxidizing catalyst, the heating source comprising: afirst reacting region including a platinum-based catalyst comprising asolid acid comprised of an inorganic oxide and a strong acid ion boundto the inorganic oxide, a platinum-based metal supported on the strongacid, and a carrier supporting the solid acid and the platinum-basedmetal; and a second reacting region including a non-platinum-basedcatalyst; and a reforming reaction part for generating hydrogen by areforming catalyst reaction.
 10. The reformer of claim 9, wherein theplatinum-based catalyst and the non-platinum-based catalyst are includedin a volume ratio of 1:1 to 1:5.
 11. The reformer of claim 9, whereinthe carrier is selected from the group consisting of Al₂O₃, TiO₂, SiO₂,ZrO₂, MgO, and combinations thereof.
 12. The reformer of claim 11,wherein the carrier is included in an amount of less than 89.5 parts byweight of the carrier based on 100 parts by weight of the platinum-basedcatalyst.
 13. The reformer of claim 9, wherein the non-platinum-basedcatalyst comprises metal oxide including CeO₂, MO wherein M is atransition element, and CuO.
 14. The reformer of claim 13, wherein the Mis selected from the group consisting of Ni, Co, Fe, and combinationsthereof.
 15. The reformer of claim 9, wherein the non-platinum-basedcatalyst includes 10 to 30 parts by weight of CeO₂, 0.1 to 5 parts byweight of MO, and 1 to 10 parts by weight of CuO, and less than or equalto 88.9 parts by weight of a carrier supporting the non-platinum-basedcatalyst, based on 100 parts by weight of the platinum-based catalyst.16. The reformer of claim 9, wherein the non-platinum-based catalystfurther comprises ZrO₂.
 17. The reformer of claim 16, wherein thenon-platinum-based catalyst includes 5 to 20 parts by weight of ZrO₂, 5to 20 parts by weight of CeO₂, 0.1 to 5 parts by weight of MO, and 1 to10 parts by weight of CuO.
 18. The reformer of claim 9, wherein thenon-platinum-based catalyst is supported on a carrier selected from thegroup consisting of Al₂O₃, TiO₂, SiO₂, cordierite, and combinationsthereof.
 19. A fuel cell system comprising: at least one electricitygenerating element for generating electrical energy by anelectrochemical reaction of hydrogen and an oxidant; a fuel supplier forsupplying a fuel to a reformer; an oxidant supplier for supplying anoxidant to the reformer and said at least one electricity generatingelement; and the reformer comprising: a heating source comprising anoxidizing catalyst for generating heat by a reaction of a fuel and anoxidant using the oxidizing catalyst, the oxidizing catalyst comprising:a solid acid comprised of an inorganic oxide and a strong acid ion boundto the inorganic oxide; a platinum-based metal supported on the solidacid; and a carrier supporting the solid acid and the platinum-basedmetal; and a reforming reaction part for generating hydrogen by areforming catalyst reaction.
 20. The fuel cell system of claim 19,wherein the heating source comprises: a first reacting region includingthe oxidizing catalyst; and a second reacting region including anon-platinum-based catalyst.